1. Field of the Invention
The present invention is related to a lane departure warning method and system thereof, and particularly to a lane departure warning method and system thereof combining a time to lane crossing (TLC) and a driver drowsiness index.
2. Description of Related Art
Transportation safety receives significant attention and the authorities around the world are stricter on the regulations of transportation safety. Hence, transportation industries around the globe enthusiastically join the development of safety technologies and safety systems to ensure driving safety of drivers. In general, safety systems for transportation are classified into passive safety systems and active safety systems. The passive safety systems include, for example, air bags, safety belts, and energy absorbing steering column; the active safety systems include, for example, adaptive cruse control, electronic stability control, emergency brake assist, lane keeping assist, and lane departure warning systems (LDWS).
Lane departure means an event of a single vehicle departing from the intended lane due to improper control from the driver. Lane departure easily leads to traffic accidents, and the faster the vehicle is moving, the shorter the time for the driver to react before the accident. If the driver is notified at some critical time in advance to increase a reaction time thereof, it is beneficial to reduce the chances of traffic accidents, thereby enhancing driving safety. Hence, the lane departure warning systems, for preventing traffic accidents caused by lane departure, are correspondingly developed.
A main function of the lane departure warning systems is to prevent a vehicle from departing from its intended lane unexpectedly. Currently, each major car manufacturer has invested significant resources in development of the lane departure warning systems, and substantial results exist. The following exemplifies a plurality of the currently used lane departure warning systems and methods. A first kind of warning system is using a camera to detect when the vehicle departs from the lane, and simultaneously using a rear sensing radar to detect the potential accident during lane changes. A second kind is a system with a camera installed on the rear-view mirror to issue audio and video warning when the vehicle departs from the original lane. The third kind of system uses a camera and a radar installed on a side of the vehicle. If it is detected that the vehicle performs dangerous actions such as departing from the lane, the driver is warned by audio signals.
Several commercial lane departure warning systems issue the warning according to whether a time to lane crossing (TLC) reaches a dangerous threshold value, wherein the time to lane crossing means a time required to elapse from the present to the future for the vehicle to possibly contact a border of the lane. Said value is an estimated value and a degree of correctness thereof seriously affects the efficiency of the warning system. Further, behaviors of the driver are quite complex, and the alertness and response speed of the driver to danger under different driver states are obviously different. For example, when the driver is talking on a cell phone, dialing the number, falling asleep or picking up an object during driving, the driver negligence level is increased and the driver cannot concentrate on driving, thereby possibly causing the vehicle to depart from the lane unexpectedly and causing an accident. The driver control behavior obviously influences the vehicle driving safety seriously. However, current commercial lane departure warning systems do not take into consideration of the driver state, and are not capable of performing appropriate adjustments corresponding to the driver state and behavior mode to achieve a warning strategy most suitable for the driver at the moment.